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Thread: Rain dilute CYA? Have I been keeping FC too high?

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    Join Date
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    Rain dilute CYA? Have I been keeping FC too high?

    Hi. I am new to the forum though I have been visiting for about 90 days and using the BBB method since that time. Thank you so much for all of the help. I found a thread on rain diluting chlorine, and a very technical article on CYA degradation, but not specifically rain.

    I feel like I am doing pretty well at BBB. In April CYA was 50-60ppm and I was keeping FC between 4-8 daily with bleach... sometimes as high as 10. Pool is beautiful, clear and better than ever. We've had about 30" of rain here in Houston since May (literally). I figure thats likely a 40% water replacement for me as depth is average probably 4-5'. I have been using an at least one 121oz jug of 8.25 bleach per day to keep it in range lately and thought it was just the rain. I tested CYA last around mid May (~50ppm). Today I tested again and it was <25 but that's a guess as 30 was the min on the Taylor test kit that I have - black dot faded but never really disappeared. Maybe it was low CYA in addition to the rain diluting Chlorine? I have pucks and dichlor from before I switched methods so I am pretty sure I know what I need to do to get it back up with what I have, but a couple of questions occurred to me

    1. Is that a reasonable reason for CYA to drop? Or is something else potentially going on?
    2. Curious if I have shouldn't have been swimming in it over the last few weeks as I have been swimming in it near shock level based on the CYA chart in pool school. No issues with equipment or comfort in the pool noticed and clothes aren't bleached out so thinking all is well but have you advised others on this before?

    My numbers this afternoon are FC=8, TC=0, pH=7.6, CYA=low (<30), TA=70, CH=240, Water Temp=90

    Thanks.
    14K gal, 12'x39' pebbletec, 2 HP pump, 60 sqft DE filter, InLine Chlorinator

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    Mod Squad pooldv's Avatar
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    Re: Rain dilute CYA? Have I been keeping FC too high?

    Yes, it is certainly possible that your cya was diluted by lots of rain. We had record rain in May also and I had to add cya 3 times. It is fine to swim with FC between minimum and shock level for your cya. We had to slam a couple of weeks ago and swam for over a week with fc in the mid 20s and cya at 70.
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    Richard320's Avatar
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    Re: Rain dilute CYA? Have I been keeping FC too high?

    Welcome!

    I wish I had your problems. You get to use pucks for a few weeks.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    DaninFLA's Avatar
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    Re: Rain dilute CYA? Have I been keeping FC too high?

    has your pool been overflowing from the rain? if so, then yes your CYA can get diluted from that. if not, the test is a bit subject as well and has a plus/minus 10ppm+ degree of accuracy.
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Join Date
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    Magnolia, TX
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    Re: Rain dilute CYA? Have I been keeping FC too high?

    Yes, there is an overflow drain and the water level has been at or above it with all of the rain. Thanks for the help.
    14K gal, 12'x39' pebbletec, 2 HP pump, 60 sqft DE filter, InLine Chlorinator

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